Out Of Memory (OOM) - I got messages on my console saying Linux was out of memory, and killed some tasks, why?

Low On Memory - My system has plenty of RAM for its workload, but very little free. Why is Linux wasting so much RAM? Where is it all going? Or, why is my system using swap when it also has plenty of free RAM?

Page Table Structure - Linux uses x86-style pagetables on all architectures. This shows how they are structured and also the Linux names for each level of the pagetables (this differs from AMD or Intel's terminology in the hardware documentation). It also shows how the pagetables are structured on powerpc where the hardware does not use them directly.